What is a memory? We study how neural activity patterns are reshaped by learning, taking advantage of the relatively simple but genetically manipulable neural circuitry in Drosophila. Our goal is to establish how synaptic plasticity affects signaling in large networks of neurons to encode associative memories

What is a memory? When we learn an association, information from two different sensory streams somehow becomes linked together. What is this link in terms of neural activity? For example, after a few bad experiences, we learn that the “green” smell of an unripe banana predicts its starchy taste. How has the neural response to that green smell changed so it becomes linked to that taste? What are the underlying mechanisms—what synapses change strength, what ion channel properties change? These are the questions that drive research in Glenn Turner’s laboratory. His team addresses these questions by tracking neural activity using a combination of different techniques. Using electrophysiological methods, they can examine individual neurons with very high resolution, monitoring synaptic strength and spiking output. They have also developed functional imaging techniques to monitor the activity of the entire set of cells in the learning and memory center of the fly brain. This comprehensive view of neural activity patterns enables them to actually predict the accuracy of memory formation in separate behavioral experiments. This year, the Turner lab was able to map the activity of a particular region of the brain that is associated with learning and memory. They found that a remarkably small number of neurons are required for flies to distinguish between odors. The Turner lab also studied the role of a specific type of cells, known as Kenyon cells, that receive input via several large claw-like protrusions. These neurons use their claws to recognize multiple individual chemicals in combination in order to remember a single scent. By examining the effects of learning-related genes on these processes, they can in the future connect their network-level view of memory formation to the underlying molecular mechanisms that govern the basic cellular and synaptic changes that drive learning.